Corrosion inhibition in condensing exchangers



A. B. HILL 2,911,351

CORROSION INHIBITION IN CONDENSING EXCHANGERS Nov. 3, 1959 Filed Sept 30, 1955 39 xmg Alfred 8. Hill INVEN TOR ATTORNEY Z,9l 1,351 Patented Nov. 3, 1959 INHIBITION IN CONDENSING EXCHANGERS Alfred B. Hill, New Orleans, La., assignor, by mesne assignments, to The American Oil Company, a corporation of Maryland Application September 30, 1955, Serial No. 537,650 3 Claims. (Cl. 208-47) CQRRQSION This invention relates to the inhibition of corrosion resulting from the action of sulfur bodies. More particularly it relates to corrosion inhibition in condensing heat exchanger service. In the distillation of petroleum distillates which normally contain sulfur compounds such as hydrogen sulfide, mercaptans. etc., the vapors are other coolants, such as liquid hydrocarbon oil, may be utilized.

A liquid corrosion inhibitor is introduced by way of conduit 21 and conduit 22 into the shell side of exchanger 12. Conduit 22 extends substantially the entire length of the tubular portion of exchanger 12, i.e., from the fixed condensed in heat exchangers having surfaces formed of ordinary carbon steel or copper or various brass alloys, particularly Admiralty metal. The sulfur bodies present in the vapors entering the condensing exchanger cause serious corrosion of the exchanger surfaces. It has become the practice in this art to introduce corrosion inhibitors which form protective films on the metal surfaces, along with the vapor stream entering the exchanger. However, very poor distribution of the corrosion inhibitor takes place with this method of injection and serious spot corrosion problems still are normally present in this service.

. An object of the invention is the inhibition of corrosion on the surfaces of condensing heat exchangers in sulfur-body containing hydrocarbon service. A particular object is a method of condensing vapors containing sulfur bodies in heat exchangers composed of ordinary steel, copper or brass wherein essentially uniform protection is given the metal surfaces. Other objects will become apparent in the course of the detailed description.

The invention is described in connection with the annexed figures which set out a preferred embodiment of the invention.

Figure 1 shows a tube and shell heat exchanger adapted for condensing service.

Figure 2 shows a segment of a distributing tube taken along the lines 22 of Figure 1.

It is to be understood that the following illustrative embodiment sets forth only one method of utilizing the instant invention and that many variations may readily be devised by those skilled in this art.

In Figure 1, hydrocarbon vapors are passed from a source not shown by way of conduit 11 into the shell side of heat exchanger 12 which is provided with a plurality of tubes 13 etc. The hydrocarbon vapors contain sulfur bodies such as hydrogen sulfide, carbonyl sulfide, mercaptans and other organo-sulfur compounds normally present in petroleum hydrocarbons or shale oil distillates or distillates obtained from coking of coal. The distillate may be any distillate which is capable of being vaporized under the conditions of operation and of being condensed in the particular heat exchanger being utilized. In this embodiment, the vapor consists of the gasoline range boiling material derived from the catalytic cracking of gas oils. The vapor contains a large amount of hydrogen sulfide and mercaptans. The vapors passed through the shell side of exchanger 12 are condensed and are withdrawn as a liquid stream by way of conduit 16. Cooling water is introduced into the tube side of exchanger 12 by way of conduit 18, passes through tubes 13 etc. and is withdrawn by way of conduit 19. Instead of water,

header 26 to about the floating header 27. Conduit 22 is provided with apertures which are preferably uniformly placed over the entire length of the conduit, i.e., the entire length of the conduit herein is understood to be that portion of the conduit within the condensing zone of exchanger 12. The apertures 29 etc. are set in such a manner that liquid corrosion inhibitor is ejected upwardly with respect to the conduit 22. Also, the apertures are preferably placed in an alternating fashion so that the liquid will be ejected upwardly and on opposite horizontal sides of conduit 22. Since conduit 22 is placed approximately the uppermost portion of the tube bundle, the liquid corrosion inhibitor will be sprayed upwardly and to the side in such a manner that all of the tubular condensing surfaces will be contacted by the liquid corrosion inhibitor which descends in the form of a fine ram. a

Figure 1 shows the preferred form of dispensing conduit. In this embodiment, one of the upper tubes in the outer circle of the tube bundle is plugged by means 31 at the floating header 27. Conduit means 21 are provided'attached to the fixed end of the tube 22 to permit the introduction of the liquid corrosion inhibitor. Apertures 29 etc. have been bored into the tube by removing it from the exchanger prior to the attachment of means 21. Figure 2 shows the arrangement of apertures 29 etc. more clearly. In Figure 2, the observer is looking at the top of conduit 29, i.e., the apertures 29 etc. are directed upwardly toward the top of the shell of exchanger 12. Apertures 29 etc. are uniformly spaced along the length of tube 29 in this particular embodiment on 3 inch centers and are set alternately so that one row of apertures ejects liquid about at an angle of from the liquid ejected from the parallel row of apertures, said parallel row being indicated in Figure 2 by aperture 290 etc. In this embodiment, apertures 29 etc. are set at an angle of about 45 from the horizontal; thereby the angle between the row of apertures designated 29 in Figure 2 and that designated 29a therein amounts to about 90. The angular setting of apertures 29 etc. may be more or less than this 45 angle but it is preferred that the setting be such that the liquid will be ejected in an upward direction. The spacing lengthwise of the apertures 29 etc. will be determined by the particular conditions existing in the particular heat exchanger.

It is believed that while the use of a tube from the tube bundle provides probably the simplest method of introducing inhibitor into the shell side of the exchanger, 21 separate conduit can be readily positioned in the exchanger by any one of the various techniques readily available to a pipe fitter.

The liquid corrosion inhibitor utilized herein may be any one of those inhibitors now widely utilized in the petroleum industry, not only for forming a semi-permanent coating on the surfaces to be protected in refinery operations, but also in the oil production art for use in protecting oil and gas wells. Numerous publications and patents have been issued on suitable liquid corrosion inhibitors. A recent publication describing many suitable liquid corrosion inhibitors which are generically described as relatively high molecular weight semipolar molecules which form inhibiting coatings on metal appear in Oil and Gas Journal, 52, 41 (February 15, 1954), pp. 148-150. Other articles concerning the use of these type of inhibitors broadly, and certain materials particularly, are set out in Oil and Gas Journal, 48, 16 (August 25, .1949), p. 96, and in Combustion, 25, 7 (January 1954), pp. 55-58. This latter article is particularly concerned with the preferred type of liquid corrosion inhibitor which is a high molecular weight amine compound commonly known in the art as a filming amine inhibitor. US. Patents 2,598,213 and 2,643,227 set out particular classes of these filming amines which are suitable for use in the process of the instant invention. An article in Petroleum Processing, 9, 8 (August 1954), pp. 1192- 1193, describes the use, in a petroleum refining operation, of a commercially available filming amine which is particularly suitable for the purpose of this invention; this article particularly points out that type of operation which applicant found to be unsatisfactory wherein the amine is injected directly into the vapor line prior to condensation. The preferred filming amines are available commercially under various trade names, for example, Kontol 118, Polyrad 110-A, and Stanolind 601.

Example A heat exchanger provided with Admiralty metal tubes was utilized in eondensing'service on the gasoline boiling range vapors from a fractionating operation of aliquid product of the catalytic cracking of gas oil containing about 1.5 percent of total sulfur. Thisexchanger handled about 125,000 pounds of vapors per hour. The material entering the exchanger was at a temperature of about 240 F. and the liquid effluent was at about 100 F. A commercial filming amine type inhibitor had been introduced into the vapor transfer line prior to the entry of the vapor into the exchanger. Under these conditions, the life of the exchanger tube bundle was about 130 days as a maximum.

The embodiment of the invention as set out in Figures 1 and 2 was introduced into this exchanger and the exchanger was then operated at about the same conditions as during the previous unsatisfactory service. About 22 gallons per day of this same commercial filming amine inhibitor was introduced for several days into the ex- 4 changer to form a protective coating following conventional practice; this was at the start of the operation on the modified exchanger. After the film had been built up, the quantity of the amine inhibitor was maintained at a substantially constant 6 gallons per day. The unit was shut down after days operation utilizing the modified corrosion inhibitor injection procedure and the tube bundle was inspected. The inspection showed that there was no noticeable corrosion of any portion of the tube bundle and that the tube bundle was ready for further operation Without any maintenance work. The mod-- ified injection procedure appeared to have'completely protected the metal surfaces without permitting the formation of even isolated spots of corrosion. v

Thus having described the invention, What is claimed is: 1. In the method of condensing vapors, comprising sulfur bodies, in a horizontally positioned heat exchanger means of the shell and tube type, wherein said vapors are condensed in the shell side of said exchanger means and the shell side surfaces of said tubes are subjected tocorrosive attack by said sulfur bodies, the improvement which comprises continuously introducing, in an upper portion of and over essentially the entire length ofthe shell side of said exchanger means, a rain-of liquid: corrosion inhibitor to afford uniform protection to essen tially the entire condensing area thereof.

2. The method of claim 1 wherein said va ore are petroleum hydrocarbons boiling above the gasoline range. 3. The method of claim 1 wherein said inhibitor is a filming amine type inhibitor.

References Cited in the file of this patent UNITED STATES PATENTS 1,715,095 Morrell et al May 28, 1929. 1,809,167 Isles Jan. 9, 1931 1,844,475 Morrell et al Feb. 9, 1932 1,959,714 Groves May 22, 1934 2,162,933 Bolinger et al June 20, 1939* 

1. IN THE METHOD OF CONDENSING VAPORS, COMPRISING SULFUR BODIES, IN A HORIZONTALLY POSITIONED HEAT EXCHANGER MEANS OF THE SHELL AND TUBE TYPE, WHEREIN SAID VAPORS ARE CONDSENSED IN THE SHELL SIDE OF SAID EXCHANGER MEANS AND THE SHELL SIDE SURFACES OF SAID TUBES ARE SUBJECTED TO CORROSIVE ATTACK BY SAID SULFUR BODIES, THE IMPROVEMENT WHICH COMPRISES CONTINUOUSLY INTRODUCING, IN AN UPPER PORTION OF AND OVER ESSENTIALLY THE ENTIRE LENGTH OF THE 